LR parsing is attractive because: LR parsing is most general non-backtracking shift-reduce parsing, yet it is still efficient. The class of grammars that can be parsed using LR methods is a proper superset of the class of grammars that can be parsed with predictive parsers. LL(1)-Grammars Ì LR(1)-Grammars An LR-parser can detect a syntactic error as soon as it is possible to do so a left-to-right scan of the input.